ITC not availed in GSTR 3B

My firm is having an eligible input tax credit on office expense (common) for the year. As 95% of our sale is non-gst sale petrol and diesel we don't plan to avail ITC for the common expense. We hope that it is ok to add the input tax portion with the office expense head in an entry as:

office exp xxx (inclusive of GST)
to. cash. xxx

please advise if there are any issues with the entry or any rules or disclosures that we are violating.