By reliability do you mean a particular measure of it, like alpha or omega? Say more what you mean by measure gaps?

I mean to say to measure gap between services or facilities. I just want to know that likert scale can be used reliably for quantifying and measuring gaps or not?

you code that data and go for alpha value in SPSS. if you get a value above 0.9 the research tools is excellent, if it is above 0.8 its good and above 0.7 its ok and if less is then 0.7 it will be not suitable for the study. Best of luck for yours research. It can used for measuring the gap in service and facilities provided that you have different set of questionnaire for service and facilities which can be easily measured by likert scale.

Thank you for your response Madhusudan Sir.. Can you suggest me which point scale is good to analyse 5 or 7 point likert scale?

Five point likely scale is good.