Well....
Technically you can't. Access isn't a word processing program. What is BOLD to a database? That and a few bucks will get you a cup of coffee at your favorite coffee house.
So....
Try this as a mind-shift.
If the "Tax from" line is fixed on the report at a certain place, make unbound text boxes with indistinct borders. Put "Tax from " in an unbound text box with normal attributes. Put [Od] in a bound text box with Bold as one of its attributes. Put the rest of the stuff in bound or unbound text boxes as needed, with normal or bold attributes as required.
Then, to make up for the indistinct borders, draw a rectangle with dark borders and a transparent center. Surround ALL of the text boxes that you made to put that string together. Be aware that you cannot expect to "trim" the string to get rid of excessive blank spaces very easily. That is because AFAIK you cannot easily tell when the text in a given text box has been occluded by the end of the box.