diff --git a/gwaspy/phasing/phase.py b/gwaspy/phasing/phase.py
index e386f35..72a01f8 100644
--- a/gwaspy/phasing/phase.py
+++ b/gwaspy/phasing/phase.py
@@ -12,6 +12,7 @@ def run_phase(backend: Union[hb.ServiceBackend, hb.LocalBackend] = None,
               fam_file: str = None,
               data_type: str = 'array',
               software: str = 'shapeit',
+              fill_tags: bool = False,
               output_filename: str = None,
               out_dir: str = None):
 
@@ -44,6 +45,7 @@ def run_phase(backend: Union[hb.ServiceBackend, hb.LocalBackend] = None,
             reference_path=ref_path,
             fam_file=pedigree,
             data_type=data_type,
+            fill_tags=fill_tags,
             output_filename=output_filename,
             output_path=out_dir)
     # else: To add BEAGLE
@@ -57,6 +59,7 @@ def main():
     parser.add_argument('--local', action='store_true')
     parser.add_argument('--billing-project', required=True)
     parser.add_argument('--data-type', type=str, default='array', choices=['array', 'wgs'])
+    parser.add_argument('--fill-tags', action='store_true')
     parser.add_argument('--software', type=str, default='shapeit', choices=['beagle', 'shapeit'])
     parser.add_argument('--output-filename', type=str, required=True)
     parser.add_argument('--out-dir', type=str, required=True)
@@ -75,5 +78,6 @@ def main():
               fam_file=args.pedigree,
               data_type=args.data_type,
               software=args.software,
+              fill_tags=args.fill_tags,
               output_filename=args.output_filename,
               out_dir=args.out_dir)
diff --git a/gwaspy/phasing/shapeit5_phase.py b/gwaspy/phasing/shapeit5_phase.py
index 41f8966..9fbcae3 100644
--- a/gwaspy/phasing/shapeit5_phase.py
+++ b/gwaspy/phasing/shapeit5_phase.py
@@ -20,12 +20,45 @@ def size(file: str):
     return size_gigs
 
 
+def annotate_vcf(
+        b: hb.batch.Batch = None,
+        vcf: hb.ResourceGroup = None,
+        region: str = None,
+        ncpu: int = 8,
+        memory: str = 'standard',
+        storage: int = None,
+        img: str = 'docker.io/lindonkambule/gwaspy_phase_impute:latest',
+) -> Job:
+    j = b.new_job(name=f'Add AC, AN tags to input: {region}')
+
+    j.image(img)
+    j.cpu(ncpu)
+    j.memory(memory)
+    j.regions(['us-central1'])
+    j.storage(f'{storage}Gi')
+
+    j.declare_resource_group(
+        annotated_vcf={
+            'vcf': '{root}.bcf',
+            'index': '{root}.bcf.csi'
+        }
+    )
+
+    j.command(f"""
+                bcftools +fill-tags {vcf['vcf']} -Ou -- -t AN,AC --output {j.annotated_vcf['vcf']}
+                bcftools index {j.annotated_vcf['vcf']} --output {j.annotated_vcf['index']} --threads {ncpu}
+                """)
+
+    return j
+
+
 def shapeit_phasing(
         batch: hb.Batch = None,
         input_path: str = None,
         reference_path: Optional[str] = None,
         fam_file: Optional[hb.ResourceFile] = None,
         data_type: str = 'array',
+        fill_tags: bool = False,
         output_filename: str = None,
         output_path: str = None):
 
@@ -244,6 +277,14 @@ def concatenate_rare_chunks(
             ref_vcf = None
             ref_size = 0
 
+        if fill_tags:
+            chrom_vcf = annotate_vcf(
+                b=batch,
+                vcf=chrom_vcf,
+                region=f'chr{i}',
+                storage=round(vcf_size*1.5 + ref_size + 2)
+            ).annotated_vcf
+
         if data_type == 'array':
             phase_common(
                 b=batch,