diff --git a/.github/workflows/automated_tests.yml b/.github/workflows/automated_tests.yml
index f63adc7..77165c0 100644
--- a/.github/workflows/automated_tests.yml
+++ b/.github/workflows/automated_tests.yml
@@ -26,4 +26,5 @@ jobs:
       run: conda config --show-sources
     - name: Run tests
       run: |
+        export NXF_VER=22.04.5
         make
\ No newline at end of file
diff --git a/Makefile b/Makefile
index 109fe6e..4c607fe 100644
--- a/Makefile
+++ b/Makefile
@@ -29,3 +29,4 @@ test:
 	bash test/scripts/run_test_11.sh
 	bash test/scripts/run_test_12.sh
 	bash test/scripts/run_test_13.sh
+	bash test/scripts/run_test_14.sh
diff --git a/README.md b/README.md
index ef731d6..1ba516b 100644
--- a/README.md
+++ b/README.md
@@ -268,6 +268,25 @@ These annotations are provided by VAFator (https://github.com/TRON-Bioinformatic
 
 No technical annotations are performed if the parameter `--input_bams` is not passed.
 
+## Phasing with WhatsHap
+
+The phase of the mutations can be inferred from the reads pileup.
+This information is relevant to determine the impact of nearby mutations.
+WhatsHap adds the phasing information when possible to the VCF following the VCF specification for that purpose.
+Genotypes with phase information use the `|` instead of the `/` and `0|1` and `1|0` represent the two different phases.
+A homozygous mutations in phase is represented as `1|1`.
+Furthermore, because phasing may be incomplete, to define the different phased blocks the INFO/PS annotation used. 
+All mutations belonging to the same phase block share the same PS number.
+
+BAM files need to be provided to perform phasing with `--input_bams` and the phasing sample has to be determined with 
+`--phasing_sample`.
+
+This approach has some limitations:
+- We only support diploid genotyped VCF files. WhatsHap does support polyploid samples. But the particular case of 
+somatic mutations is not supported.
+- The sample name chosen to perform the phasing has to be the same across all VCFs. 
+Not to be mistaken with the patient name. Eg: only `normal` samples across all patients can be used for phasing
+
 ## Functional annotations
 
 The functional annotations provide a biological context for every variant. Such as the overlapping genes or the effect 
diff --git a/main.nf b/main.nf
index 92497f7..6c3c616 100755
--- a/main.nf
+++ b/main.nf
@@ -6,10 +6,13 @@ include { FILTER_VCF } from './modules/01_filter'
 include { BCFTOOLS_NORM; VT_DECOMPOSE_COMPLEX; REMOVE_DUPLICATES } from './modules/02_normalization'
 include { SUMMARY_VCF; SUMMARY_VCF as SUMMARY_VCF_2 } from './modules/03_summary'
 include { VAFATOR; MULTIALLELIC_FILTER } from './modules/04_vafator'
-include { VARIANT_ANNOTATION_SNPEFF; VARIANT_ANNOTATION_BCFTOOLS } from './modules/05_variant_annotation'
+include { WHATSHAP } from './modules/05_phasing'
+include { VARIANT_ANNOTATION_SNPEFF; VARIANT_ANNOTATION_BCFTOOLS } from './modules/06_variant_annotation'
+
 
 params.help= false
 params.input_vcfs = false
+params.input_bams = false
 params.input_vcf = false
 
 // optional VAFator inputs
@@ -32,6 +35,7 @@ params.skip_multiallelic_filter = false
 // SnpEff input
 params.snpeff_organism = false
 params.snpeff_datadir = false
+params.phasing_sample = false
 
 
 if (params.help) {
@@ -136,6 +140,10 @@ workflow {
             final_vcfs = MULTIALLELIC_FILTER(final_vcfs)
             final_vcfs = MULTIALLELIC_FILTER.out.filtered_vcf
         }
+        if (params.phasing_sample) {
+            WHATSHAP(final_vcfs.join(input_bams.groupTuple()))
+            final_vcfs = WHATSHAP.out.phased_vcf
+        }
     }
 
     if (params.snpeff_organism) {
diff --git a/modules/05_phasing.nf b/modules/05_phasing.nf
new file mode 100644
index 0000000..b0713c3
--- /dev/null
+++ b/modules/05_phasing.nf
@@ -0,0 +1,33 @@
+params.phasing_sample = false
+params.cpus = 1
+params.memory = '3g'
+
+
+process WHATSHAP {
+    cpus params.cpus
+    memory params.memory
+    tag "${patient_name}"
+    publishDir "${params.output}/${patient_name}", mode: "copy"
+
+    conda (params.enable_conda ? "bioconda::whatshap=1.4" : null)
+
+    input:
+    tuple val(patient_name), file(vcf), val(bams)
+
+    output:
+    tuple val(patient_name), file("${patient_name}.phased.vcf"), emit: phased_vcf
+
+    script:
+    phasing_bams = bams.toList().stream()
+        .filter{ b -> b.split(':')[0] == "${params.phasing_sample}" }
+        .collect{ b -> b.split(":")[1] }
+        .join(" ") ;
+    """
+    whatshap phase \
+    --indel \
+    -o ${patient_name}.phased.vcf \
+    --reference=${params.reference} \
+    ${vcf} \
+    ${phasing_bams}
+    """
+}
\ No newline at end of file
diff --git a/modules/05_variant_annotation.nf b/modules/06_variant_annotation.nf
similarity index 95%
rename from modules/05_variant_annotation.nf
rename to modules/06_variant_annotation.nf
index b469ae1..c79115e 100644
--- a/modules/05_variant_annotation.nf
+++ b/modules/06_variant_annotation.nf
@@ -49,6 +49,7 @@ process VARIANT_ANNOTATION_BCFTOOLS {
         --fasta-ref ${params.reference} \\
         --gff-annot ${params.gff} ${vcf} \\
         --output-type v \\
-        --output ${name}.annotated.vcf
+        --output ${name}.annotated.vcf \\
+        --phase a
     """
 }
diff --git a/nextflow.config b/nextflow.config
index bcea7da..d608e48 100644
--- a/nextflow.config
+++ b/nextflow.config
@@ -27,7 +27,7 @@ env {
 // Capture exit codes from upstream processes when piping
 process.shell = ['/bin/bash', '-euo', 'pipefail']
 
-VERSION = '2.5.0'
+VERSION = '3.0.0'
 
 manifest {
   name = 'TRON-Bioinformatics/tronflow-vcf-postprocessing'
@@ -87,6 +87,7 @@ Optional input:
     * --snpeff_memory: for some samples SnpEff may require to use more memory (default: 3g)
     * --mapping_quality: VAFator minimum mapping quality (default: 0)
     * --base_call_quality: VAFator minimum base call quality (default: 0)
+    * --phasing-sample: enables phasing with whatshap and defines the sample BAM to phase the VCF (BAMs need to be provided)
 
 Output:
     * Normalized VCF file
diff --git a/test/data/test_input_single_sample.txt b/test/data/test_input_single_sample.txt
new file mode 100644
index 0000000..e221c35
--- /dev/null
+++ b/test/data/test_input_single_sample.txt
@@ -0,0 +1 @@
+single_sample	test/data/test_single_sample.vcf
\ No newline at end of file
diff --git a/test/scripts/run_test_14.sh b/test/scripts/run_test_14.sh
new file mode 100644
index 0000000..e8857ee
--- /dev/null
+++ b/test/scripts/run_test_14.sh
@@ -0,0 +1,16 @@
+#!/bin/bash
+
+
+source test/scripts/assert.sh
+output_folder=test/output/test14
+echo -e "tumor_normal\tprimary:"`pwd`"/test/data/TESTX_S1_L001.bam" > test/data/test_bams.txt
+echo -e "tumor_normal\tnormal:"`pwd`"/test/data/TESTX_S1_L002.bam" >> test/data/test_bams.txt
+echo -e "single_sample\ttumor:"`pwd`"/test/data/TESTX_S1_L001.bam" >> test/data/test_bams.txt
+echo -e "single_sample\ttumor:"`pwd`"/test/data/TESTX_S1_L002.bam" >> test/data/test_bams.txt
+echo -e "single_sample\tnormal:"`pwd`"/test/data/TESTX_S1_L001.bam" >> test/data/test_bams.txt
+echo -e "single_sample\tnormal:"`pwd`"/test/data/TESTX_S1_L002.bam" >> test/data/test_bams.txt
+
+nextflow main.nf -profile test,conda --output $output_folder --input_bams test/data/test_bams.txt \
+  --phasing_sample normal --input_vcfs test/data/test_input_single_sample.txt
+
+test -s $output_folder/single_sample/single_sample.phased.vcf || { echo "Missing test 10 output file!"; exit 1; }